【3D Scanning Knowledge】What is 3D Scanning Accuracy? - SHINING 3D Scanner Buying Guide
When discussing 3D scanners, a frequently mentioned concept is 3D scanning accuracy. How do you understand the concept of 3D scanning accuracy? What is the difference between accuracy, precision, and volumetric accuracy? If you are confused by these professional 3D scanning terms, then this article is for you!
Simply put, the most common 3D scanning terms are:
【Efficiency of 3D Scanning】 - It affects "the speed of the scanning process"
• Point Distance
• Frame Rate (FPS)
• Field of View (FOV)
• Object Size
【Accuracy of 3D Scanning】 - It affects "the error between the 3D object and the actual object" and "the quality of the scanned object"
• Accuracy
• Precision
• Volumetric Accuracy
This article will discuss "the error between the 3D object and the actual object" and "the quality of the scanned object" (For "3D scanning efficiency or speed", please refer to: 【3D Scanning Knowledge】4 Tips to Improve 3D Scanning Efficiency!)
Accuracy vs. Precision vs. Volumetric Accuracy
When taking measurements, accuracy and precision must be considered, as they indicate how close a measured value is to a recognized or established value. The International Organization for Standardization (ISO) calls this "Accuracy (Trueness and Precision) of Measurement Methods and Results," defining accuracy as a combination of random errors and systematic errors. For applications such as automotive modification and industrial manufacturing, accurate data is very important.
Accuracy
Under certain measurement conditions, the degree of deviation of the estimated value from its true value in multiple measurements of a single instance. It can also be understood as "the degree to which the measurement result approaches the true value."
Precision
Under certain measurement conditions, the degree of dispersion among various measured values in multiple measurements of a single instance. "Lower precision means greater standard deviation."
Source : SHINING 3D
Volumetric Accuracy
A formula precisely tested and calculated that shows the error relationship between measured values and true values when the volume of a scanned model changes.
Most 3D scanner manufacturers also specify volumetric accuracy, which is the accuracy of several captures, and the global accuracy decreases as the size of the scanned part increases.
For example: 0.05mm + 0.15mm/m.
According to the example, if your part is 2 meters long, the scanner's accuracy will be 0.05 + (0.15*2) = 0.35mm. This is a significant difference compared to the original single-scan accuracy! Therefore, especially if you are scanning large objects (such as cars), volumetric accuracy is more important than single-scan accuracy.
Source: Aniwaa
• Some 3D scanners with integrated photogrammetry modules can use scanning alignment markers to build the 3D architecture of an object before filling it. Markers are precise reference points for the 3D scanner, like connecting the dots. By using the "architecture" from photogrammetry, your data will be more accurate.
• Photogrammetry is a 3D scanning technology that involves taking multiple photos of an object from different angles to calculate its shape and size.
Factors Affecting Measurement Accuracy
Regardless of the manufacturer or market positioning, the accuracy of 3D scanners will fluctuate due to various factors such as temperature, data integrity, algorithms, and scanning angle. Therefore, it is essential to understand how to prevent accuracy deviations and obtain the most reliable and accurate 3D data.
1. Temperature
To ensure optimal scanning accuracy, allowing the scanner to warm up and maintain a stable temperature is also critical. Once the temperature is stable, calibration should be performed before scanning to achieve optimal accuracy. The sequence of warming up, stabilizing temperature, calibrating, and scanning will yield the most accurate results.
2. Data Integrity
Data integrity is an important factor affecting accuracy. Incomplete data can lead to inaccurate or distorted results, affecting the overall quality of 3D information. Therefore, it is essential to ensure the completeness and authenticity of the data to obtain the most accurate results.
Incomplete data
Complete data
Complete data
3. Algorithm
From calibration to data processing, algorithms play a crucial role in 3D data collection. It is a set of complex mathematical formulas that ensure accurate reconstruction of scanned objects. Calibration is also an important part of this process, ensuring the accuracy of the scanner and providing the necessary data for the algorithm to function correctly.
4. Scanning Angle
Ideally, the scanner should be as perpendicular to the object as possible. This positioning helps the scanner extract markers more accurately, leading to more precise 3D data.
Scanning with FreeScan UE
Cumulative errors in scanning larger objects can be greater. However, there are some scanning methods that can help reduce errors, such as "global markers" and "photogrammetry."
Global Markers
Before scanning the point cloud, we can first scan global markers. This allows the algorithm to optimize accuracy and obtain more precise data, ultimately improving volumetric accuracy.
Photogrammetry
Photogrammetry can improve the accuracy of global marker data. We can import an appropriate scale file and, depending on the size of the scanned object, place matching scales near the object before scanning. Generally, photogrammetry is suitable for measuring large components in industrial applications that require high precision. Of the two methods, photogrammetry is considered superior to global markers.
Scanning an aircraft model using photogrammetry
Comparison Table of Measurement Accuracy for SHINING 3D Metrology Grade 3D Scanners
For objects requiring high precision and being small in size, two models are recommended: AutoScan Inspec and OptimScan-5M Plus. Autoscan Inspec is fully automated and easier to use, while Optimscan-5M plus can handle slightly larger objects than the Autoscan Inspec.
High precision and high detail applications
How should we choose the FreeScan series? If we need to scan larger objects with high precision requirements, we can choose the FreeScan UE Pro, as it is equipped with photogrammetry capabilities, which can greatly reduce errors during the alignment process.
FreeScan UE 11 Application
FreeScan UE Pro Application
FreeScan UE Pro Application
Finally, let's talk about the FreeScan Trak. This scanner is different from others because it does not require markers to be attached to the scanned object. If it is difficult to attach markers to some large objects, this scanner can be considered.
Now that you are familiar with accuracy, precision, and volumetric accuracy, but still confused about SHINING 3D's scanners?
▶Click here to filter out suitable 3D scanner recommendations◀ (Links to SHINING 3D official website)
Many different terms often appear on manufacturers' websites and specification sheets. What truly matters is volumetric accuracy and mesh resolution, and how they meet your specific needs.
Although technical specifications for accuracy and resolution are helpful for easily and quickly comparing different 3D scanners, they should not be the only decisive factors. You should also consider factors such as brand certification, history, software, and after-sales service.
If you have difficulty choosing a 3D scanner, or are unsure what your company's case (and budget) actually needs?
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